The Precision Approach Path Indicator, or PAPI, is a well-known and established approach landing aid to provide visual glide slope guidance to approaching aircraft. Aviation authorities have established specific requirements for the behavior of this system; these specifications are codified in both US and International standards. The United States Federal Aviation Administration standards for PAPI systems are in Advisory Circular AC 150/5345-28F. Requirements include, but are not limited to, a light housing assembly that can project a specific pattern of red and white light. Those skilled in the art know that among these requirements are a broad sector that is white in color, and a broad sector that is red in color. Furthermore these red and white sectors have to cover specific angular areas in both elevation and azimuth. In addition the white sector, which is on top, and the red sector, on the bottom, must have a very sharply defined horizontal boundary between the two colors.
In current embodiments this arrangement of projected light is accomplished with a lens that has the same optical power in both the horizontal and vertical axis. A design using such a lens has a very limited area for the light source to be located; furthermore the light source must be substantially similar in both horizontal and vertical extent. Designs of this nature are limited in the total number, and therefore intensity, or Light Emitting Diodes which can be imaged by a single lens. Designs of this type may be found in current commercial production. In addition a design of this nature is taught by Tian et al USP Application 20100123398. This restriction has practical ramifications in terms of limited brightness and high local heat. The design of Tian maintains this two-dimension optical geometry and does not provide relief from the limited brightness and heat dissipation issues of the standard design.